Multifunction copiers and network scanners have appeared and these devices can be used to freely exchange images with computers via a network. Recently, devices have also been announced that support multiple network and communications protocols so that a single entered image can be broadcast to multiple destinations by using different protocols. However, there are also devices that are capable of exchanging only monochrome images depending on the communication protocol, as is the case with facsimile machines. In view of such instances, the same document is read as both a color image and a monochrome image and either the color or monochrome image is sent in accordance with the communication protocol.
A scanner with an automatic density adjustment function executes image processing in which prescanning is performed and the background level is made white before the next scan starts. The reading of an image after the prescan in such a scanner is limited to the reading of color or monochrome image. As a consequence, if an automatic density adjustment is applied when the same document is read as a color image and as a monochrome image, it is necessary to perform prescanning before the color image is read and prescanning before the monochrome image is read. Reading the image therefore takes time.